Method and device for executing HARQ in TDD-based wireless communication system

Abstract

A method is provided for performing a hybrid automatic repeat request (HARQ) by a user equipment (UE). An uplink (UL) grant for a first subframe of a second serving cell is received through a first serving cell. UL data in the first subframe of the second serving cell is transmitted according to the UL grant. When a not-acknowledgement (NACK) for the UL data is received through a physical HARQ indicator channel (PHICH) in a subframe i of the first serving cell, the UE performs a non-adaptive retransmission for the UL data in a second subframe of the second serving cell. When a PHICH resource corresponding to the UL data is not present in the subframe i, the UE does not perform the non-adaptive retransmission in the second subframe of the second serving cell.

What is claimed is: 
     
       1. A method for performing a hybrid automatic repeat request (HARQ) by a user equipment (UE), the method comprising:
 receiving, through a first serving cell, an uplink (UL) grant for a first subframe of a second serving cell; and 
 transmitting UL data in the first subframe of the second serving cell according to the UL grant, 
 wherein when a not-acknowledgement (NACK) for the UL data is received through a physical HARQ indicator channel (PHICH) in a subframe i of the first serving cell, the UE performs a non-adaptive retransmission for the UL data in a second subframe of the second serving cell, and 
 wherein when a PHICH resource corresponding to the UL data is not present in the subframe i, the UE does not perform the non-adaptive retransmission in the second subframe of the second serving cell. 
 
     
     
       2. The method of  claim 1 , wherein the UE is configured with a plurality of serving cells comprising the first serving cell and the second serving cell. 
     
     
       3. The method of  claim 1 , wherein the first serving cell and the second serving cell use different uplink-downlink (UL-DL) configurations, and each of the UL-DL configurations is information on which each subframe within a time division duplex (TDD) TDD frame is configured as a UL subframe, a DL subframe or a special subframe. 
     
     
       4. The method of  claim 1 , wherein if a UL grant for the second subframe is received through a physical downlink control channel (PDCCH) in the subframe i, the UE performs a transmission according to the UL grant for the second subframe. 
     
     
       5. The method of  claim 4 , wherein the UE performs a new transmission or a retransmission according the UL grant for the second subframe regardless of content of the PHICH in the subframe i. 
     
     
       6. A user equipment (UE), comprising:
 a Radio Frequency (RF) unit configured to transmit and receive radio signals; and 
 a processor connected with the RF unit, 
 wherein the processor is configured to:
 control the RF unit to receive, through a first serving cell, an uplink (UL) grant for a first subframe of a second serving cell, and 
 control the RF unit to transmit UL data in the first subframe of the second serving cell according to the UL grant, 
 
 wherein when a not-acknowledgement (NACK) for the UL data is received through a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH) in a subframe i of the first serving cell, the UE performs a non-adaptive retransmission for the UL data in a second subframe of the second serving cell, and 
 wherein when a PHICH resource corresponding to the UL data is not present in the subframe i, the UE does not perform the non-adaptive retransmission in the second subframe of the second serving cell. 
 
     
     
       7. The UE of  claim 6 , wherein the UE is configured with a plurality of serving cells comprising the first serving cell and the second serving cell. 
     
     
       8. The UE of  claim 6 , wherein the first serving cell and the second serving cell use different uplink-downlink (UL-DL) configurations, and each of the UL-DL configurations is information on which each subframe within a time division duplex (TDD) frame is configured as a UL subframe, a DL subframe or a special subframe. 
     
     
       9. The UE of  claim 6 , wherein if a UL grant for the second subframe is received through a physical downlink control channel (PDCCH) in the subframe i, the UE performs a transmission according to the UL grant for the second subframe. 
     
     
       10. The UE of  claim 9 , wherein the UE performs a new transmission or a retransmission according the UL grant for the second subframe regardless of content of the PHICH in the subframe i.